CLIMATE CHANGE - scientific
The topics of global warming and climate change have arguably been one of the most studied and
debated issues of the last 60 or more years. Is the Earth getting warmer? Is warming of the Earth
related to natural events or it is brought on by anthropogenic causes? How will climate change affect
us? Is it just a myth brought on by flawed and incomplete science?
Over the past half century, answering these questions has turned climate change into a highly debated
issue. However, further investigation into current research has led the scientific community to
extensively agree that the climate is changing and that evidence points to anthropogenic (human)
reasons (Oreskes, 2004).
To further investigate climate change, one would need to know the facts about the greenhouse effect.
The greenhouse effect is not just a theory.
Solar energy arrives to us through energy waves called radiation. Much of the radiation makes its way
to the Earth’s surface and warms the Earth. This radiation will then re-radiate back into the
atmosphere. As it re-radiates back in the form of infra-red radiation, its wavelength becomes longer.
The original shorter wavelengths pass easily through the atmosphere, however, much of this new longer
wavelength gets absorbed or trapped by greenhouse gases and heats the Earth’s atmosphere (Daniel,
1999).
We can look to the solar system to further illustrate the greenhouse effect. Mercury, being the closest
planet to the Sun, has one of the highest daytime temperatures of any planet in the solar system.
Daytime temperatures on Mercury can reach upwards of 800oF. However, without an atmosphere to
trap solar energy, Mercury’s nighttime temperatures can reach almost -200oF. This is an unparalleled
temperature difference between day time and night time. (Mercury: Facts & Figures. NASA)
If you would investigate temperatures on Venus, you would find a different scenario. Venus’ position in
the solar system averages 50 million kilometers further from the Sun than Mercury’s, however, Venus is
hotter than Mercury. Day time temperatures on Venus can be over 850oF. Night time temperatures on
Venus remain about the same as day time temperature. This is because Venus has an incredibly thick
atmosphere dominated by greenhouse gases. Venus has an atmosphere 93 times thicker than that of
the Earth’s. Ninety -six percent of Venus’ atmosphere is dominated by carbon dioxide (Venus: Facts and
Figures. NASA). This thick atmosphere, comprised mainly of strong greenhouse gases, is the reason for
its incredible surface temperature and little variation between day and night.
According to some studies, the Earth’s average temperature would be at least 91 degrees F (33 degrees
Celsius) lower without the Greenhouse Effect (Smil, 2003). As mentioned above, the Greenhouse Effect
helps keep the Earth warm and thriving.
So where is the problem? In order for the Earth’s temperature to remain stable, its heat budget needs
to be in balance. Overall the Earth must have the same amount of energy leave through the
atmosphere as enters for average temperatures to remain constant. Greenhouse gases have proven to
trap solar energy, and therefore, an increase in greenhouse gases in the Earth’s atmosphere will create
an increase in global temperatures. This creates the event you have known to be called global warming.
The Intergovernmental Panel on Climate Change (IPCC) is a scientific body supported by the United
Nations designed to assess published literature and be the internationally accepted authority on climate
change. The IPCC has published 5 major reports that will be referred to throughout this reading.
In its latest Fifth Assessment Report (AR5), the IPCC stated in their “Summary for the Policy Makers”
that: Human influence has been detected in the warming of the atmosphere and the oceans, in changes
in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in
some climate extremes. This evidence for human influence has grown since AR4. It is extremely likely
that human influence has been the dominant cause of the observed warming since the mid-20th century
(IPCC, 2013).
In its fourth assessment (AR4) published in 2007, the IPCC reported that scientists were more than 90%
certain that most global warming was being cause by an anthropogenic increase in carbon dioxide (IPCC,
2007). In 2013, the IPCC stated that the major cause of global warming is carbon dioxide emissions from
the combustion of fossil fuels, cement production and land use changes such as deforestation (IPCC,
2013).
According to the IPCC, global warming is the unequivocal and continuing rise in the average
temperature of Earth's climate system (IPCC, 2013). In approximately the last 100 years, the Earth’s air
and sea surface temperatures have risen about 0.8 °C (1.4 °F). About two thirds of this increase has
occurred since 1980 (The National Academies Press, 2011). During each of the last three decades it has
been warming at a rate greater than any since 1850 (IPCC, 2013).
In AR5, using predictions from climate models, the IPCC indicated that global surface temperature will
continue to rise. Using the lowest emission scenario, the report predicted a further rise of 0.3 to 1.7 °C
(0.5 to 3.1 °F) throughout the 21st century. In the highest emission scenario, temperatures rose an
unprecedented 2.6 to 4.8°C (4.7 to 8.6°F) (IPCC, 2013).
According to the IPCC, greenhouse gas emissions increased 2.2% per year between 2000 and 2010.
Compare this to a 1.3% increase per year in the period between 1970 to 2000 (IPCC, 2013). Under the
scientific assumption that an anthropogenic increase in greenhouse gases has been and will continue to
lead to an increase in global surface temperatures, it can be concluded that global temperature will
continue to rise.
CLIMATE CHANGE
– in the articles
Glaciers are melting, sea levels are rising, cloud forests are dying, and wildlife is scrambling to keep pace.
It has become clear that humans have caused most of the past century's warming by releasing heattrapping gases as we power our modern lives. Called greenhouse gases, their levels are higher now than
at any time in the last 800,000 years.
We often call the result global warming, but it is causing a set of changes to the Earth's climate, or longterm weather patterns, that varies from place to place. While many people think of global warming and
climate change as synonyms, scientists use “climate change” when describing the complex shifts now
affecting our planet’s weather and climate systems—in part because some areas actually get cooler in
the short term.
Climate change encompasses not only rising average temperatures but also extreme weather events,
shifting wildlife populations and habitats, rising seas, and a range of other impacts. All of those changes
are emerging as humans continue to add heat-trapping greenhouse gases to the atmosphere, changing
the rhythms of climate that all living things have come to rely on.
What will we do—what can we do—to slow this human-caused warming? How will we cope with the
changes we've already set into motion? While we struggle to figure it all out, the fate of the Earth as we
know it—coasts, forests, farms, and snow-capped mountains—hangs in the balance.
Understanding the greenhouse effect
The "greenhouse effect" is the warming that happens when certain gases in Earth's atmosphere trap
heat. These gases let in light but keep heat from escaping, like the glass walls of a greenhouse, hence
the name.
Sunlight shines onto the Earth's surface, where the energy is absorbed and then radiate back into the
atmosphere as heat. In the atmosphere, greenhouse gas molecules trap some of the heat, and the rest
escapes into space. The more greenhouse gases concentrate in the atmosphere, the more heat gets
locked up in the molecules.
Scientists have known about the greenhouse effect since 1824, when Joseph Fourier calculated that the
Earth would be much colder if it had no atmosphere. This natural greenhouse effect is what keeps the
Earth's climate livable. Without it, the Earth's surface would be an average of about 60 degrees
Fahrenheit (33 degrees Celsius) cooler.
In 1895, the Swedish chemist Svante Arrhenius discovered that humans could enhance the greenhouse
effect by making carbon dioxide, a greenhouse gas. He kicked off 100 years of climate research that has
given us a sophisticated understanding of global warming.
Levels of greenhouse gases have gone up and down over the Earth's history, but they had been fairly
constant for the past few thousand years. Global average temperatures had also stayed fairly constant
over that time—until the past 150 years. Through the burning of fossil fuels and other activities that
have emitted large amounts of greenhouse gases, particularly over the past few decades, humans are
now enhancing the greenhouse effect and warming Earth significantly, and in ways that promise many
effects, scientists warn.
Aren't temperature changes natural?
Human activity isn't the only factor that affects Earth's climate. Volcanic eruptions and variations in solar
radiation from sunspots, solar wind, and the Earth's position relative to the sun also play a role. So do
large-scale weather patterns such as El Niño.
But climate models that scientists use to monitor Earth’s temperatures take those factors into account.
Changes in solar radiation levels as well as minute particles suspended in the atmosphere from volcanic
eruptions, for example, have contributed only about two percent to the recent warming effect. The
balance comes from greenhouse gases and other human-caused factors, such as land use change.
The short timescale of this recent warming is singular as well. Volcanic eruptions, for example, emit
particles that temporarily cool the Earth's surface. But their effect lasts just a few years. Events like El
Niño also work on fairly short and predictable cycles. On the other hand, the types of global
temperature fluctuations that have contributed to ice ages occur on a cycle of hundreds of thousands of
years.
THINGS HUMANS ARE DOING THAT CONTRIBUTE TO GLOBAL WARMING
LIST OR SOMETIHNG LIKE THAT